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논문 : 기계적 성질 ; Ll2 (Al, Cr)3 Ti기 2상 금속간화합물의 소성거동에 미치는 V 및 Zr 첨가의 효과
박정용 ( Jeong Yong Park ),오명훈 ( Myung Hoon Oh ),위당문 ( Dang Moon Wee ) 대한금속재료학회 ( 구 대한금속학회 ) 1998 대한금속·재료학회지 Vol.36 No.7
Effects of V and Zr additions on the microstructures and the mechanical properties of two-phase intermetallic compounds consisting of LI2 matrix and 20vol.% Cr2Al were investigated. Among the V-added two-phase intermetallic compounds, Al-2lTi-20Cr-3V showed the best ductility as well as relatively high yield strength. V was found to substitute for Cr and improve the ductility of Cr2Al phase, In the case of Zr-added two-phase alloys, the particle size of Cr2Al was refined, and Zr was found to be soluble only in Li matrix As Zr content increased in the Zr-added two-phase alloys, the yield strength increased, but the ductility decreased. It was found in Zr-added two-phase alloys that the loss of ductility in Li matrix due to Zr additions was more significant than the ductilizing effect due to second phase refinement. Zr-added two-phase alloys, however, shoed higher yield strength than V-added two-phase alloys over the entire temperature range tested. Based on the results obtained, plastic deformation behavior of two-phase intermetallic compounds alloyed with V and Zr were examined. Al-19Ti-21Cr-2V-2Zr showed the best mechanical properties among the alloys tested, which is suggested to be the alloy composition to optimize the effects of V and Zr additions simultaneously.
압력용기용 Ni-Mo-Cr계 고강도 저합금강의 P, Mn 함량에 따른 템퍼 취화거동 및 입계편석거동 평가
박상규 ( Sang Gyu Park ),김민철 ( Min Chul Kim ),이봉상 ( Bong Sang Lee ),위당문 ( Dang Moon Wee ) 대한금속·재료학회 2010 대한금속·재료학회지 Vol.48 No.2
Higher strength and fracture toughness of reactor pressure vessel steels can be obtained by changing the material specification from that of Mn-Mo-Ni low alloy steel (SA508 Gr.3) to Ni-Mo-Cr low alloy steel (SA508 Gr.4N). However, the operation temperature of the reactor pressure vessel is more than 300℃ and the reactor operates for over 40 years. Therefore, we need to have phase stability in the high temperature range in order to apply the SA508 Gr.4N low alloy steel for a reactor pressure vessel. It is very important to evaluate the temper embrittlement phenomena of SA508 Gr.4N for an RPV application. In this study, we have performed a Charpy impact test and tensile test of SA508 Gr.4N low alloy steel with changing impurity element contents such as Mn and P. And also, the mechanical properties of these low alloy steels after longterm heat treatment (450℃, 2000hr) are evaluated. Further, evaluation of the temper embrittlement by fracture analysis was carried out. Temper embrittlement occurs in KL4-Ref and KL4-P, which show a decrease of the elongation and a shifting of the transition curve toward high temperature. The reason for the temper embrittlement is the grain boundary segregation of the impurity element P and the alloying element Ni. However, KL4-Ref shows temper embrittlement phenomena despite the same contents of P and Ni compared with SC-KL4. This result may be caused by the Mn contents. In addition, the behavior of embrittlement is not largely affected by the formation of M3P phosphide or the coarsening of Cr carbides.
Ni/Ni<sub>3</sub>Al 단결정의 냉간압연 거동에 미치는 결정방위 및 석출물의 영향
송성훈 ( S. H. Song ),위당문 ( D. M. Wee ),박노진 ( No-jin Park ),오명훈 ( Myung-hoon Oh ) 한국열처리공학회 2020 熱處理工學會誌 Vol.33 No.1
In this study, thin foil fabrication using Ni/Ni<sub>3</sub>Al single crystal was performed by cold-rolling. It was found that the cold-rolling behavior was strongly dependent on the initial crystallographic orientation rather than morphology of Ni<sub>3</sub>Al precipitates. The deformation banding was formed in the case of (100)[001]- and (210)[001]- oriented specimens at 83% reduction in thickness. However, the effects of Ni<sub>3</sub>Al precipitates morphology on the microstructure evolution of Ni/Ni<sub>3</sub>Al single crystals during cold-rolling were not so serious comparing with the effects of initial crystallographic orientation. Therefore, it could be concluded that the deformation behavior of Ni/ Ni<sub>3</sub>Al single crystals at serious strain level was strongly dependent on the initial crystallographic orientation rather than the morphology of Ni<sub>3</sub>Al precipitates, whereas the initial deformation behavior was related to both crystallographic orientation and the morphology of Ni<sub>3</sub>Al precipitates. (Received December 9, 2019; Revised December 17, 2019; Accepted December 27, 2019)
RF Magnetron Sputtering에 의한 금속간화합물 TiAI 모재위의 AI-21Ti-23Cr 고온내산화코팅
박상욱,박정용,이호년,오명훈,위당문,Park, Sang-Uk,Park, Jeong-Yong,Lee, Ho-Nyeon,O, Myeong-Hun,Wi, Dang-Mun 한국재료학회 1996 한국재료학회지 Vol.6 No.7
Ti-48AI(at.%) 모재위에 RF magnetron sputtering을 이용하여 AI-21Ti-23Cr(at.%) 조성의 박막을 코팅하였다. RF power 200W, 증착압력 0.8Pa, 증착온도 573k에서 증착된 시편의 가장 우수한 고온재산화성을 나타내었다. 573K에서 증착된 AI-21Ti-23Cr 코팅층은 증착시에는 비정질을 형성하나 산화시험동안 결정화가 진행되며, 표면에는 치밀한 ${Al}_{2}{O}_{3}$층이 형성되었다. 573K에서 코팅된 시편에 대하여 1073K, 1173K 및 1273K에서 100시간동안 등온산화시험을 실시하였다. 무게증량곡선은 모든 온도에서 parabolic law를 따르는 안정된 산화거동을 보였으며 이와같은 산화특성은 표면에 치밀한 ${Al}_{2}{O}_{3}$층이 형성되었기 때문인 것으로 판단된다. 1273K에서 산화시험 후 코팅층의 기지는 고온산화에 따른 AI원자의 소모와 모재로부터의 Ti원자의 확산에 의해 TiAICr상을 형성하였으며, 무게증량은 낮은 온도에 비해 다소 크게 증가하는 경향을 나타내었다. Ti-48Al(at.%) specimens were coated with Al-21Ti-23Cr(at.%) film by RF magnetron sputtering. Ti-48Al specimen coated at 200, 0.8Pa and 573K showed the best oxidation resistance property in the isothermal oxidation test. Al-21Ti-23Cr film was amophous after depostion, but crystallized and fromed a protective ${Al}_{2}{O}_{3}$ layer on the surface during oxidation. Ti-48Al specimens coated at 573K have been sassessed by isothermal oxidation test for 100 hours at 1073K, 1173K and 1273K. The mass gain curves showed that parabolic stage continued at al tested temperature range in isothermal oxidation test, and the excellent oxidation resistance is attriutable to the formation of a protective ${Al}_{2}{O}_{3}$ layer on the surface of Al-21Ti-23Cr film. After oxidation test at 1273K, the matrix of Al-21Ti-23Cr film had transformed into TiAlCr phase due to the depletion of Al during oxidation and the diffusion of Ti from the substrate, and the extent of mass gain of the specimen increased compared with that of specimens tested at lower temperature.
논문 : 압력용기용 Ni-Mo-Cr계 고강도 저합금강의 합금원소 함량 변화에 따른 미세조직학적 특성변화의 열역학 계산 및 평가
박상규 ( Sang Gyu Park ),김민철 ( Min Chul Kim ),이봉상 ( Bong Sang Lee ),위당문 ( Dang Moon Wee ) 대한금속재료학회 ( 구 대한금속학회 ) 2008 대한금속·재료학회지 Vol.46 No.12
An effective way of increasing the strength and fracture toughness of reactor pressure vessel steels is to change the material specification from that of Mn-Mo-Ni low alloy steel(SA508 Gr.3) to Ni-Mo-Cr low alloy steel(SA508 Gr.4N). In this study, we evaluate the effects of alloying elements on the microstructural characteristics of Ni-Mo-Cr low alloy steel. The changes in the stable phase of the SA508 Gr.4N low alloy steel with alloying elements were evaluated by means of a thermodynamic calculation conducted with the software ThermoCalc. The changes were then compared with the observed microstructural results. The calculation of Ni-Mo-Cr low alloy steels confirms that the ferrite formation temperature decreases as the Ni content increases because of the austenite stabilization effect. Consequently, in the microscopic observation, the lath martensitic structure becomes finer as the Ni content increases. However, Ni does not affect the carbide phases such as M23C6 and M7C3. When the Cr content decreases, the carbide phases become unstable and carbide coarsening can be observed. With an increase in the Mo content, the M2C phase becomes stable instead of the M7C3 phase. This behavior is also observed in TEM. From the calculation results and the observation results of the microstructure, the thermodynamic calculation can be used to predict the precipitation behavior.
Cr 첨가 $\textrm{Ll}_2\textrm{Al}_3\textrm{Ti}$기 2상 금속간화합물의 시효처리 효과
이재경,박정용,오명훈,위당문,Lee, Jae-Gyeong,Park, Jeong-Yong,O, Myeong-Hun,Wi, Dang-Mun 한국재료학회 1999 한국재료학회지 Vol.9 No.10
$Ll_2$기지에 20 vol.% $\textrm{Cr}_{2}\textrm{Al}$이 석출된 Al-21Ti-23Cr 2상합금은 $1150^{\circ}C$에서는 2상영역에 위치하지만 $1000^{\circ}C$에서는 3상영역에 위치한다. 이러한 점에 착안하여 본 연구에서는 Al-21Ti-23Cr 2상합금의 시효처리시 $800^{\circ}C$ 및 $1000^{\circ}C$이하에서 시효처리하여 $Ll_2$기지에 제3상을 미세하게 석출시켜, 기계적성질을 개선하고자 하였다. Al-21Ti-23Cr 2상합금의 시효처리시 $800^{\circ}C$ 및 $1000^{\circ}C$에서는 $Ll_2$기지부분에 수 $\mu\textrm{m}$ 크기의 제3상이 다량 석출되지만 $600^{\circ}C$이하에서는 제3상이 석출이 관찰되지 않았으며, 제3상의 석출형태는 $1000^{\circ}C$보다 $800^{\circ}C$에서 시효처리할 경우 더욱 미세하게 분포하는 것으로 확인되었다. 시효온도 상승에 따른 Al-21Ti-23Cr 2상합금의 항복강도는 $800^{\circ}C$에서 급격히 증가 후 다시 급격히 감소하는경향을 나타냈으며, 이러한 항복강도의 급격한 증가는 $Ll_2$기지 부분에 수 $\mu\textrm{m}$ 크기의 미세한 제3상이 다량 석출되기 때문에 나타나는 현상으로 판단된다. Al-21Ti-23Cr 2상합금의 시효처리시 $Ll_2$기지에 석출되는 제3상은 TiAlCr으로 확인되엇으며, 이러한 TiAlCr 석출상의 이용은 $Ll_2$기지의 균열전파에 대한 저항성를 향상시켜 합금의 기계적성질의 개선에 매우 효과적일 것으로 판단된다. Two-phase Al-21Ti-23Cr alloy containing 20 vol.% $\textrm{Cr}_{2}\textrm{Al}$ as a second phase in the $Ll_2$ matrix is located in the two- phase region of the Al- Ti- Cr phase diagram at $1150^{\circ}C$, while in the three-phase region at $1000^{\circ}C$. Based on this result, the mechanical properties of the A1-21Ti-23Cr alloy were enhanced through the refined precipitation of the third phase in the $Ll_2$ matrix by aging the alloy below $1000^{\circ}C$. It was observed that a several ,m of the third phase precipitated in the $Ll_2$ matrix through aging at $800^{\circ}C$ and $1000^{\circ}C$, but the precipitation was not observed below $600^{\circ}C$. Furthermore, the third phase was more finely precipitated at $800^{\circ}C$ than at $1000^{\circ}C$. Although the third phase precipitated at $800^{\circ}C$ and at $1000^{\circ}C$, the compressive yield strength increased rapidly at $800^{\circ}C$ only. This is probably attributable to the refined precipitation of the third phase in the $Ll_2$ matrix. It is expected that the precipitation of the third phase. which was confirmed to be the TiAlCr phase, improves the mechanical properties by preventing crack propagation in the $Ll_2$ matrix.
Ni-Mo-Cr계 저합금강의 천이온도영역에서의 파괴인성에 미치는 Ni 및 Cr 함량의 영향
이기형 ( Ki Hyoung Lee ),박상규 ( Sang Gyu Park ),김민철 ( Min Chul Kim ),이봉상 ( Bong Sang Lee ),위당문 ( Dang Moon Wee ) 대한금속·재료학회 2009 대한금속·재료학회지 Vol.47 No.9
Materials used for a reactor pressure vessel(RPV) are required high strength and toughness, which determine the safety margin and life of a reactor. Ni-Mo-Cr low alloy steel shows better mechanical properties than existing RPV steels due to higher Ni and Cr contents compared to the existing RPV steels. The present study focuses on effects of Ni, Cr contents on the cleavage fracture toughness of Ni-Mo-Cr low alloy steels in the transition temperature region. The fracture toughness was characterized by a 3-point bend test of precracked Charpy V-notch(PCVN) specimens based on ASTM E1921-08. The test results indicated that the fracture toughness was considerably improved with an increase of Ni and Cr contents. Especially, control of Cr content was more effective in improving fracture toughness than manipulating Ni content, though Charpy impact toughness was changed more extensively by adjusting Ni content. These differences between changes in the fracture toughness and that in the impact toughness were derived from microstructural features, such as martensite lath size and carbide precipitation behavior.